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394                                           THE EAR

otosclerosis is a very common disease, the atypical cases must amount in all
to a considerable number. If sensorineural deafness begins early in life in a
member of a family in which other well-marked cases of otosclerosis are
present, and if there be no other probable cause for the nerve deafness, the
case should be regarded as one of otosclerosis.

In certain families there is a tendency for the hearing to deteriorate before
the age at which presbyacusis is usually found.


Neurofibroma of the eighth nerve arises from the neurilemma (Schwann
sheath) in the most lateral part of the internal auditory meatus. It is a benign
tumour which usually grows very slowly, interfering with the function of the
auditory and vestibular nerves, but later occupying the cerebellopontine
angle of the posterior fossa (Fig. 209).

Other lesions occurring in the cerebellopontine region include meningioma,
angioma, epidermoid and aneurysm, but the acoustic neurofibroma is the
commonest tumour found in the posterior cranial fossa.
Changes in the Labyrinth. The first stage appears to be a fibrinous exudation
(choked labyrinth), with atrophy of the cochlear ganglion and Corti's organ
{Fig. 210). Later the exudate becomes organized into myxomatous tissue, in
which new bone formation may be seen.

SYMPTOMS. The age of onset is usually 30-50 years. The clinical history may
be divided into three stages: (1) Initial or 'otological', in which the patient
suffers from tinnitus, deafness, giddiness, loss of balance and nystagmus.
This stage ends with the occurrence of headache which is worst at night. (2)
Intermediate or 'neurological* stage, with headache, and involvement of
neighbouring nerves, producing loss of the corneal reflex, numbness over
the cheek and slight weakness of the masseter muscle on the affected side
(fifth), diplopia (sixth) and facial paralysis (seventh). Later there is dimness
of vision (choked disk), dysphagia and thickness of speech, with muscular
hypotonia and dysdiadokokinesia on, and tendency to fall to, the side of the
lesion. The so-called 'cerebellar seizures' or vagal attacks are a distressing
feature. They may be preceded by giddiness, headache and dimness of vision.
At first the patient is conscious during attacks, but later he is unconscious.
The pupils are dilated, with stertorous breathing and rapid, irregular pulse.
Jerkings of the head and extremities are followed by general rigidity. The
attacks may be accompanied by vomiting. They have been attributed to
excessive tension in the lateral cistern in which the tumour lies, or to com-
pression of the middle cerebellar peduncle. (3) Terminal stage, with weakness
of sphincter control, delirium, dementia, Cheyne-Stokes respiration and


The Cochlear Apparatus. Sensorineural deafness varying from slight to
total deafness may be found. Normal hearing is found in less than 1 per cent
of proved acoustic neurofibroma. There is absence of loudness recruitment
in 90 per cent of cases in which deafness is still of moderate degree. Speech
discrimination is poor. Abnormalities may be demonstrated by electro-
cochleography and the stapedial reflex may be reduced.